Visible Light Waves Visible light
waves are the only electromagnetic waves we can see. We see these waves as the
colors of the rainbow. Each color has a different wavelength. Red has the
longest wavelength and violet has the shortest wavelength. When all the waves
are seen together, they make white light. When white light shines through a
prism, the white light is broken apart into the colors of the visible light
spectrum. Water vapor in the atmosphere can also break apart wavelengths
creating a rainbow. Each color in a rainbow corresponds to a different
wavelength of electromagnetic spectrum.

It is easy to see that the sky is
blue. The light from the Sun looks white. But it is really made up of all
the colors of the rainbow.

A prism is a specially shaped
crystal. When white light shines through a prism, the light is separated into
all its colors.

All light travels in a straight
line unless something gets in the way to--

reflect it (like a mirror)

bend it (like a prism)

or scatter it (like
molecules of the gases in the atmosphere)

Sunlight reaches Earth's atmosphere
and is scattered in all directions by all the gases and particles in the air.
Blue light is scattered in all directions by the tiny molecules of air in
Earth's atmosphere. Blue is scattered more than other colors because it
travels as shorter, smaller waves. This is why we see a blue sky most of the
time.

Closer to the horizon, the sky fades
to a lighter blue or white. The sunlight reaching us from low in the sky has
passed through even more air than the sunlight reaching us from overhead. As the
sunlight has passed through all this air, the air molecules have scattered and
rescattered the blue light many times in many directions. Also, the surface of
Earth has reflected and scattered the light. All this scattering mixes the
colors together again so we see more white and less blue.

Why do we see rainbows in the sky?

A rainbow is an optical and
meteorological phenomenon that causes a spectrum of light to appear in the sky
when the Sun shines onto droplets of moisture in the Earth's atmosphere. They
take the form of a multi-colored arc, with red on the outer part of the arch and
violet on the inner section of the arch. A rainbow spans a continuous spectrum
of colors. Traditionally, however, the sequence is quantised. The most commonly
cited and remembered sequence, in English, is Newton's sevenfold in order from
longest to shortest wavelength: red, orange, yellow, green, blue, indigo and
violet.

"Roy G. Biv" and "Richard Of York
Gave Battle In Vain" are popular mnemonics. Rainbows can be caused by other
forms of water than rain, including mist, spray, and dew.

Sunlight contains many different
colors. Normally, we see all the colors mixed together as white light. We see a
rainbow when sunlight separates into bands of different colors. These bands of
red, orange, yellow, green, blue, indigo, and violet light are also known as the
visible spectrum.

A rainbow is created when sunlight
passes through raindrops. Light travels through different substances at
different speeds. When light travels through water, it slows down. The reduced
speed causes light to bend or refract.

To understand how a rainbow is made,
it is helpful to understand how a prism works. A prism is a triangular shaped
piece of glass. The path of a light beam changes as it goes through a prism.
Glass slows the speed of light. When light travels through a prism, it is
refracted once while going in and again as it passes through. The refraction
separates white light into its many colors.

A water drop acts like a prism.
Light refracts as it enters and leaves a drop of water. The refracting light is
separated into the colors of the spectrum. When the sky is filled with drops of
water, a rainbow is created. Light that enters the drops is refracted.
Refraction makes each color visible in its own band. Each color of the spectrum
has a slightly different wavelength. The different wavelengths bend in slightly
different ways. Long wavelengths bend the least, while short wavelengths refract
the most. Red light has the longest wavelength and violet light has the
shortest. The other colors have wavelengths that fall between. Because color
refraction is consistent, the colors of the rainbow or any other spectrum look
the same and appear in the same order. We use the memory device ROYGBV (Roy G.
Biv) to signify the order of colors.

The combination of all the separated
colors creates the beautiful arching rainbow. Since light needs to pass through
the raindrops, rainbows are always seen in the part of the sky opposite the Sun.
We see the colors of a typical rainbow as light comes from our Sun. Any star
similar to our Sun would create a rainbow with the same colors. Light from
different types of stars would create different colored rainbows, some that we
couldn't even see with our eyes. Astronomers study how a star's light separates.
This separation is called the star's spectrum.

Some Interesting Facts about
Rainbows

When you see a
rainbow...

it is
after rain. The sun is always behind you and the rain in front of you
when a rainbow appears, so the center of the rainbow's arc is directly
opposite the sun.

Most people
think...

the only
colors of a rainbow are red, orange, yellow, green, blue, indigo, and
violet, but a rainbow is actually made up of an entire continuum of
colors—even colors the eye can't see!

We are able to see
the colors of a rainbow because...

light of
different colors is refracted when it travels from one medium, such as
air, and into another- -in this case, the water of the raindrops. When
all the colors that make up sunlight are combined, they look white,
but once they are refracted, the colors break up into the ones we see
in a rainbow.

Every person...

sees their
own "personal" rainbow. When you look at one, you are seeing the light
bounced off of certain raindrops, but when the person standing next to
you looks at the same rainbow, they may see the light reflecting off
other raindrops from a completely different angle. In addition,
everyone sees colors differently according to light and how their eyes
interpret it.

You can never...

actually
reach the end of a rainbow, where a pot of gold supposedly awaits. As
you move, the rainbow that your eyes see moves as well, because the
raindrops are at different spots in the atmosphere. The rainbow, then,
will always "move away" at the same rate that you are moving.

Data compiled from The
British Antarctic Study, NASA, Environment Canada, UNEP, EPA and
other sources as stated and credited Researched by Charles
Welch-Updated daily This Website is a project of the The Ozooe Hole
Inc. http://www.theozonehole.com